The present invention relates generally to methods of connecting batteries to electronic components, and more particularly, to a method of connecting battery leads to a current collector of a polymer electrolyte cell or battery.
Improvements in microelectronics have increased the demand for electrolyte battery cells that can be directly incorporated into electronic devices so as to produce a portable, self-contained product. Some of these products are designed such that the electrolyte battery cell may be attached directly to an electronic circuit within the product.
The leads of such batteries are typically flat strips of copper that are attached to current connectors of the cell by conventional techniques, such as resistance welding or soldering. The battery leads are often connected to short tabs that extend from the current collectors of the battery cell. Such tabs are typically formed of copper or aluminum mesh or screen. Making connections between mesh tabs and flat, metallic strips by welding or soldering is particularly difficult because the connection is made very near to the layered components forming the cell.
U.S. Pat. No. 6,056,185 to Daroux et al. entitled: METHOD OF CONNECTING BATTERIES TO ELECTRONIC CIRCUITS, discloses attaching a metal lead to a current collector tab of a polymer battery by an ultrasonic welding process. The disclosed process includes positioning a collector tab extending from a polymer electrolyte battery onto one side of a flexible, metal lead and then clamping and ultrasonically welding the metal lead to the current collector.
In some applications, the aforementioned one side, surface-to-surface weld is not sufficient to prevent peeling and/or separation of the metal battery lead from the flexible metal connector.
The present invention provides an improved method of connecting copper or aluminum leads of a battery to current collectors of a polymer electrolytic cell.
In accordance with a preferred embodiment of the present invention, there is provided a method of connecting a generally flat battery lead to a current collector of a polymer battery, comprising the steps of.
bending a generally planar lead about at least one generally planar current collector tab to form a layered area, wherein at least one planar tab is disposed between planar portions of the lead with the lead wrapped around one edge of at least one tab;
clamping the layered area between two weld fixtures of an ultrasonic welder; and
vibrating the weld fixtures to ultrasonically weld together the battery lead and at least one current collector.
It is an object of the present invention to provide a method for attaching generally flat, metallic leads to a current collector tab of electrochemical cells or batteries, especially Li-ion batteries, and most especially Li-ion-polymer batteries.
Another object of the present invention is to provide a method as described above for securing copper or aluminum lead to a current collector.
Another object of the present invention is to provide a method as described above that does not require special coating or plating steps.
A still further object of the present invention is to provide a method as described above that utilizes ultrasonic welding to join a flat, metallic lead to a current collector.
A still further object of the present invention is to provide a method as described above that provides better connection between a flat, metallic lead and a current collector tab.
These and other objects will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings.